The numerical computation of gas flows with non-equilibrium thermodynamics and chemistry is considered. Several thermodynamic models are discussed, including an equilibrium model, a general non-equilibrium model, and a simplified model based upon vibrational relaxation. Flux-splitting procedures are developed for the fully-coupled inviscid equations involving fluid dynamics, chemical production, and internal energy relaxation processes. New forms of flux-vector split and flux-difference split algorithms valid for non-equilibrium flow, are embodied in a fully coupled, implicit, large-block structure. Several numerical examples in one space dimension are presented, including high-temperature shock tube and nozzle flows. © 1990.